An early example of a prior art locking key may be found in U.S. Pat. No. 3,270,792, issued Sept. 6, 1966 to Neuschotz et al. The initial mounting or tang portion of the Neuschotz locking key embodies a complete interference fit for retaining the key in a slot of the insert prior to installation. Recurring problems with this type of tang portion configuration include increased driving forces being required in order to install a key having an excessive interference fit due to poor quality manufacturing of either the key or the insert slot. Oftentimes such problems require costly reworking of the slot to correct such problems. Such reworking may be prohibitive because of either the added cost or time to accomplish such.
Subsequent to the '702 patent, improvements in the tang portion configuration were attempted in order to overcome the problems of the complete interference fit. U.S. Pat. No. 3,447,356 issued June 3, 1969 and U.S. Pat. No. 3,537,118 issued Nov. 3, 1970 to Neuschotz are illustrative of such attempts. In the '356 patent the tang portion of the locking key is shown with a configuration which reduces the amount of surface area providing the necessary interference fit. The '118 patent shows a related attempt to accomplish the same result. Unfortunately those attempts and other prior art efforts did not and have not eliminated the driveability problems associated with the original interference fit tang portions. And even when such problems were overcome, other problems would typically arise such as obstructions, e.g. burrs, in the insert slot which in and of themselves would prevent the proper installation of the locking key relative to the slot. This in turn would prevent the key from being completely driven into the carrier material.
Despite the presence of problems, inserts with locking keys continue to enjoy a market demand. Satisfying such demand with a quality, reliable product has led to the development of the present invention. The present invention is an improved tang configuration for the locking key which will overcome many, if not all, of the recurring problems of the conventional prior art interference fit designs.